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Cytotoxic T cellsA cytotoxic T cell is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.

There are billions of T cells within our blood – one teaspoon full of blood alone is believed to have around 5 million T cells, each measuring around 10 micrometres in length, about a tenth the width of a human hair. Each cell is engaged in the ferocious and unrelenting battle to keep us healthy.

The cells, seen in the animation as orange or green amorphous ‘blobs’ move around rapidly, investigating their environment as they travel. When a cytotoxic T cell finds an infected cell or, in the case of the animation, a cancer cell (blue), membrane protrusions rapidly explore the surface of the cell, checking for tell-tale signs that this is an uninvited guest.

The T cell binds to the cancer cell and injects poisonous proteins known as cytotoxins (red) down special pathways called microtubules to the interface between the T cell and the cancer cell, before puncturing the surface of the cancer cell and delivering its deadly cargo.

Animation:The time-lapse footage was created by stitching together microscopic slices of the killer cells and their quarry, according to a written statement released by the University of Cambridge. It shows T cells (orange or green blobs) encountering cancer cells (blue blobs) and injecting them with lethal proteins known as cytotoxins (red).